The motor generator functions as an electric motor by being coupled to a driving shaft, while it is capable of collecting a generated electric energy as a regenerative energy by charging it into a battery (an electrical storage device), by functioning as an electrical generator as a rotational shaft rotates in conjunction with that driving shaft.
This regenerative energy is collected as an electric energy that generates electricity by rotating a rotational shaft of a motor generator, so that a load for rotating that rotational shaft can be utilized as a regenerative braking force, and it has been utilized by mounting a regenerative control device on various devices that mount that motor generator as a power source by making it function as an electric motor.
For this motor generator, not only a case of being mounted on a device singly, but also a case of being mounted on a hybrid motor vehicle which uses it as a power source by making it function as a motor generator, along with an internal combustion engine, the so called engine (hereafter also referred to simply as an engine), that utilizes the combustion energy of gasoline and the like. In this hybrid motor vehicle, the driving speed is decelerated by using a degenerative braking force due to making that motor generator function as an electrical generator by the regenerative control device, along with a hydraulic braking force according to a friction force generated by a hydraulic control device (for example, Patent Document 1).
Note that the motor generator has an output characteristic that generates the maximum torque in a low speed driving region where the number of revolutions is small, in the case of functioning as an electric motor, and it has a relatively small torque in a high speed driving region where the number of revolutions is large. Also, it is similar for the regenerative braking force, and as shown in FIG. 10, the regenerative braking force is set to be zero at a speed by which the motor vehicle can be stopped quickly, for example, a speed range at a level of driving by the so called creep phenomenon.